A Glitch In The Sytem
by Opre999
Summary: Lucida finds herself in a world where Undertale actually happened. Just her luck that in this new world, her house is now Frisk's. It's up to Sans and Frisk to get her back home.
1. Chapter 1

**Disclaimer: I do not own Undertale, Toby Fox does.**

 **Additional Information: In this story, Frisk is a 15-year-old female. The main character is 13 years old.**

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I turn the shower off and wring out my long, brown hair. My hands wrap my mop into a hat with the towel. I put on my pajamas and other useful clothing then procced to towel dry my dripping wet hair. The lights in the house are off so I know that my parents are sleeping by now. I walk across the hall into my room to see that the only things remain is the furniture. Even my bed had been stripped to only a single white pillow on the mattress and frame.

This room that used to be mine, was barely mine at all. I was about to explore some more to see if there was even a hint of my existence when the door under me slammed close. The darkness consumed me as I shut myself in my small walk-in closet. Sitting in the farthest corner, I was hyperventilating. I could hear footsteps climb up the stairs that were right near my room. My panic attack gets even worse as the person or people walk up to the closet. I fear my life as the closet door opens.

The only thing I heard before passing out was, "hey kiddo, c… calm down."

My eyes immediately open to find myself on my blank bed. I sit up, glancing at the figure at the edge of the bed. It was leaning against the wall with its feet hanging off the side. I noticed that I was curled into a ball so the figure wasn't actually sleeping on my legs. In the mirror across from me, the figure had its right eye open and was looking at me through the mirror. The weirdest thing was, his pupil sort of glowed in the dark, much like in cartoons. There is only one person I know that can do that, Sans the skeleton. A character straight out of Undertale is on my bed, my favorite character to say the least.

He sat up and turned to face me. "morning sleeping beauty. how are you _feline_?" Sans asked, pointing to the cats on my pajama pants.

"I am feeling pretty good, thanks to your _humerus_ pun. You are very punny!" I respond, feeling much better than before. Sans starts to chuckle quietly.

"so, uh. hello, i'm sans. you are?"

"Lucida. You can call me Lucy if you want."

"alright lucy." Sans says before putting on his serious face. "what are you doing in this house?" I tremble at his tone and remember him calling me a dirty brother killer after my failed attempt at the genocide route. Warm tears flow down my face from the horrible things that I had made Frisk do that one time. Sans noticed my tears and pulled me into a hug. You would think a hug from a skeleton would be uncomfortable but, it wasn't.

"kiddo, you look like you know more than you let on. got some explaining to do but for now, let's go have breakfast."

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 **Sorry for the short chapter, the next ones will be much longer. I guess you could call this an introductory chapter for the story. Please feel free to give feedback!**


	2. Chapter 2

**Alright, here is a longer chapter. Enjoy!**

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"Where is Papyrus?" I ask when we make it downstairs. Sans gives me a suspicious look from the words that had come out of my mouth. Realization slaps me in the face and I just give Sans a dumbfounded look.

"well, this is toriel's and frisk's house. the room we were in is their guest room, i usually sleep there if i stay over." Sans explains then looks slightly hesitant. "you know who they are, don't you?"

"Y… yes." I stutter. "Would you like me to explain mysel-" I get cut off by the noise of someone rushing downstairs.

"Morning Sans! Is that the girl who was in the closet? Nice pajamas!" I turn to the voice to see Frisk, wearing athletic gear.

"Going out for a run?" I ask.

"Yeah! How'd you know?" Frisk questions. I was about to tell her when Sans spoke up.

"lucy here, knows a lot more than she lets on."

"That has nothing to do with the timelines or the multiple universes. In this neighborhood, many people go running in the morning. Simple logic." Both Sans and Frisk stare at me. If only I could keep my big mouth shut. I'm getting so excited but, I don't blame myself. If you watched as much comic dubs and play the game as much as I have, you would kind of want to pinch yourself in this situation.

"How… how much do you know?" Frisk asks, pulling me back into reality.

"Enough to scare the crap out of you guys, if I haven't already." I stare at my feet. Why do I have to spill out all of my thoughts? I usually keep them under control. "If I know Toriel, she is going to be up soon. Since I am going to spill, let's go somewhere private. The Void or Grillby's, your pick. Oh, and you better leave a note." I tell Sans with a serious tone. My information is going to reach ears no matter what I do. Might as well take control of the situation so I can make sure of which ears pick up the information.

"grillby's. you know where it is?" Sans questions.

"Chances are, it's near the Harris Teeter." I respond. Yet again Sans and Frisk stare at me. These questions are too easy to answer, much like Mettaton's quiz when Frisk first met him. "Are we taking a shortcut?"

"kiddo, you are seriously creeping me out. but i can tell that you don't want a bad time." Sans says as he pulls me to the front door.

"I'll meet you guys there. If I am going to eat a burger at 6:30 in the morning, I am sure as hell that I will run first." Frisk tells us as we disappear into nothingness.

We walk into Grillby's with a passion. All of the usuals stare at me, probably because the only other human that they have seen in here was Frisk. Sans brings me to the bar and orders a bottle of ketchup.

"And for the human?" Grillby asks.

"eggs and bacon, grillbz." Sans replies. Strangely, eggs and bacon were exactly what I wanted. Seems like I am not the only one who can guess pretty well. Grillby drops off the order and goes to serve another customer, continuously keeping eye contact with me. I pick up a piece of bacon and take a large bite. I could only guess that this bacon was from a holy pig, it was so good. Perfectly cooked and cut. I swear that my eyes were watering from the flavor. I try to enjoy every bite but my breakfast disappears so fast. I am incredibly satisfied. My attention turns to Grillby, I give him a big smile and a thumbs up. I could hear a sigh of relief flow throughout the restaurant. Turns out, the whole place was watching my reaction. Even Lesser Dog had taken himself away from his poker game to watch me.

Grillby walks over to our seats and introduces himself. He holds out his hand and I become very hesitant. "Don't worry, your skin won't burn." As a demonstration, he puts his hand on the table.

"Isn't that fireproof wood?" I ask. Grillby starts to blush and pulls out an oven mitt. I properly shake his hand now that I know for sure that my skin won't burn.

"Nice to meet you Grillby, I am Lucy. Thank you for making such delicious food!" I finally say. Grillby nods, walks away, and then the majority of the restaurant freezes in time. Only me and Sans can still move.

"so, kiddo. you know that you are still wearing pajamas, right?" Sans points out.

"I don't really have any other clothes at this point so might as well ignore it."

"makes sense. let's cut to the chase, how do you know so much about this universe, about the timelines? wait, i have a better question for you. what was the name of the famous skeleton detective?"

"Oooh. I haven't heard this one. Hmm…. You?"

"nope. guess again" There was only one other skeleton I knew of that could fit the script.

"W.D Gaster?" Sans nearly dropped his ketchup bottle from my response.

"n… nope kiddo, the correct answer was sherlock bones." He looks distraught and then tries to cover it up by laughing at his own pun. "just tell me already kiddo, i am on the edge of my seat. How do you know so much?"

"Where I come from, your lives were literally a game. The playable character was Frisk and the player follows and controls her through the Underground. Chances are in this world, Frisk took the true pacifist route and never reset again. There is also the neutral route, regular pacifist route, and the genocide route. After the game had some fans, people started making comics and animations. Most of them included you. Fanfictions were also made, causing ships to rise up. You are either paired with Frisk or Toriel if you are not alone." I pause to observe his reaction. Sans stiffens his back and interrupts me before I can continue. His gaze is set on something behind me.

"yeah… yeah… that's nice kiddo… but, we got to move NOW!" He pushes me off the stool and throws me into a corner of the room. All goes black but, I can still see Sans. He is in the distance…. uh... FIGHTING ANOTHER SANS?! I run over to him to get a better look but a wall of bones stops me.

"ki… kiddo… go on without me. you gotta run! try to find an exit to this place okay? i won't let you get hurt." I hear his voice over the whooshing of attacks coming from his direction. A corridor of bones line up behind me. I fight my urge to run through the bones, knowing that they could easily kill me if I run into too many of them at once. If Sans is trying to keep me safe by using his magic, he will soon tire out. I have to something! My feet pound on the ground as I run deep into the bone-maze. Hopefully I will find some food somewhere, right? Then I notice, Megalovania plays louder in the area to the right. To the left, I can hear Bonetrousle playing. I stop to find a glass of tea lying on the floor. Checking its info I find that it is a modified version of Sea Tea. It cannot give me HP but it will give me eight times as much speed! I quickly drink it and dash off to the left.

Bonetrousle blazes in my ears until I come to a screeching stop. I nearly fall trying to not run over Core Frisk. I have no Idea why she is here but, at least I know how to stop.

"Hello Lucida. It's nice to meet you in person." She almost offers a ghostly white hand out for me to shake but, she decides against it. "What's inside you is the only way to save Sans from…." She fades away before she can finish her sentence. I wasn't expecting to see her but I decide to ponder on what she had said. Well what is inside me? There are organs, bones, and blood. Although, could she be talking about something else? And then I remember, it's my soul! I lightly pull on the warm feeling in my chest. A green, perfectly shaped heart hovers over my hands. I scrape the back of my mind remembering that green objects during battles either heal or protect. Creating a muffin, I run straight to the right. Running through the endless walls of bones, I heal myself over and over again. Megalovania gets so loud that my eardrums almost pop. I slow down nearing the last few walls. I can see the fight from where I stand and I stop.

Not only is Error the one fighting Sans, Blueberry, (Sans from Underswap) has his soul tied in Error's strings. I observe from the fight that whenever Sans lands a hit on Error, Error's HP doesn't lower. Blueberry looks as worn out as Sans, hanging literally by a thread. I can only guess that Error is using Blueberry as means of healing since he is much kinder than me. Time to make a dramatic entrance. I punch my left hand into my right, crack my neck on both sides, and roll back my shoulders to give a devastating and also a relieving set of cracks. Error and Sans waste no time on looking at me with a shocked face. The bone-maze collapses behind me. Maybe I was too dramatic? Blueberry manages to turn his head enough to flash me a big smile, causing my soul to glow brighter. Error realizes that I can heal as well as Blueberry and sends his blue strings right my way. I run just fast enough to dodge them until I make it to Sans.

Sans nearly passes out from exhaustion when I finally reach him. A Gaster Blaster appears and slowly opens its jaws. I throw myself over Sans to protect him. And then everything goes white.


End file.
